RIBONUCLEIC ACIDS APPEARING DURING THE PROCESS OF CHLOROPLAST REGENERATION IN THE “GLUCOSE-BLEACHED” CELLS OF CHLORELLA PROTOTHECOIDES1

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Abstract
Investigations were made on the modes of synthesis of different species of RNA which appear during the greening (chloroplast regeneration) of the “glucose-bleached” cells of Chlorella protothecoides containing profoundly degenerated plastids. RNAs were extracted from the algal cells which had been labelled with 32P for 1 hr before harvesting at different stages of the greening in the light and in darkness, and subjected to column chromatography with methylated albumin-coated kieselguhr. It was found that, during the greening process, the elution profiles of RNAs, in terms of the optical density at 260 mμ and 32P-radioactivity, changed profoundly. Based on these and other results, it was concluded that during an early phase of the chloroplast regeneration in the glucosebleached algal cells, there occurs an active formation of both ribosomal RNAs (rRNAs) and the RNAs corresponding to soluble RNA (sRNA), the formation coming, however, later to a standstill when the synthesis of chlorophyll has proceeded to a certain level. The quantity ratio of sRNA to rRNA was found to be constant (30:70) at different stages of the greening (both in the light and in darkness), with a few exceptions. The synthesis of the chloroplast ribosomal RNA is markedly accelerated by light, and its maximum rate is observed sometime later than that of the non-chloroplast (“cytoplasmic”) ribosomal RNA. It was suggested that there are at least two different sites of synthesis of ribosomal RNAs, one in the plastid and the other outside of it (most probably in the nucleus).